155. The unit of frequency of an A.C. signal is

A. cycle

B. cycle-sec

C. hertz/sec

D. hertz

156. Which of the following values of alternating voltage should an insulation absolutely withstand?

A. The average value

B. The r.m.s. value

C. The peak value

D. Half the effective value

157. An A.C. voltage is impressed across a pure resistance of 3.5 ohms in parallel with a pure inductance of impedance of 3.5 ohms,

A. the current through the resistance is more

B. the current through the resistance is less

C. both resistance and inductance carry equal currents

D. none of the above

158. In a pure inductive circuit if the supply frequency is reduced to 1/2, the current will

A. be reduced by half

B. be doubled

C. be four times as high

D. be reduced to one fourth

159. In a pure capacitive circuit if the supply frequency is reduced to 1/2, the current will

A. be reduced by half

B. be doubled

C. be tour times at high

D. be reduced to one fourth

160. The relation between the apparent power, actual power and reactive power is given by

A. Apparent power= actual power + reactive power

B. Apparent power= actual power ? reactive power

C. Apparent power= il(actual power)2 ?(reactive power)2

D. Apparent power= ?/(actual power)2 + (reactive power)2

161. When an alternating current passes through an ohmic resistance the electrical power converted into heat is

A. apparent power

B. true power

C. reactive power

D. none of the above

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